In general, a signal processing procedure for wireless communication consists of channel coding, modulation, frequency up-conversion, and transmission in a transmitting side. In accordance therewith, signal processing in a receiving side consists of frequency down-conversion, demodulation, and channel decoding. Herein, the demodulation in the receiving side includes a procedure of calculating a per-bit or per-symbol decoding metric.
To generate the decoding metric, it is necessary to premise a specific probability distribution for an interference and noise signal. Techniques of the related art assume a Gaussian distribution for an interference signal to perform decoding with a low complexity. Therefore, a Quadrature Amplitude Modulation (QAM)-series modulation scheme is primarily used in order for the interference signal to be similar to a Gaussian signal to the maximum extent possible.
However, it is generally known that a channel which assumes a non-Gaussian distribution has a greater channel capacity than a channel which assumes the Gaussian distribution. Therefore, if decoding is performed properly, the channel which assumes the non-Gaussian distribution can have a higher decoding performance in comparison with the channel which has the Gaussian distribution.
Accordingly, there is a need to develop a modulation scheme which allows an interference signal to be similar to the non-Gaussian distribution to the maximum extent possible, and as a result, a Frequency-QAM (FQAM) scheme is proposed. The FQAM method is a hybrid modulation scheme in which the QAM scheme is combined with a Frequency Shift Keying (FSK) scheme, and has advantages of the QAM scheme having a high spectral efficiency and the FSK scheme allowing an interference signal to have a non-Gaussian distribution.
The FQAM is further evolved to Multi Tone-FQAM (MT-FQAM) in which MT-FSK for expressing FSK symbols is combined with the QAM by using multi-tones of the symbol. Due to the multi-tones of the symbol, the MT-FQAM has a gain property superior to the FQAM. Such a gain property of the MT-FQAM is caused by a diversity effect of multi-tones constituting one MT-FSK symbol.
Accordingly, there is a need for an apparatus and a mapping for considering a diversity effect when mapping a tone of an MT-FQAM symbol to a frequency resource.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure.